This invention relates to a process of refining edible oil rich in naturally occurring carotenes and Vitamin E whereby substantially a large percentage of the naturally occurring carotenes and Vitamin E is retained in the refined oil. More particularly the invention relates to a process of refining palm oil whereby substantially a large percentage of the naturally occurring carotenes and Vitamin E is retained in the refined oil.
It is a known fact that crude palm oil is rich in carotenes-a class of C40 polyunsaturated hydrocarbons. Commercially cultivated oil palm yield crude palm oil which contains 500-700 ppm carotenes of which .alpha. and .beta. carotenes from 90% of the total carotenes. However, newer clones or new species of oil palm trees can produce crude palm oil with carotene concentrations of 1000-3000 ppm. The carotenes are known to possess pro-vitamin A properties and recent findings have shown that .beta.-carotene also inhibits tumor progression and hence reduce cancer formation in animals, including humans. At present edible palm oil is used in the refined, bleached and deodorized form. However, the refining process of producing refined, bleached and deodorized form of oil commonly adopted in palm oil refining industry results in the carotenes being destroyed while the oil is being deodorized and deacidified. The refined oil of the prior art process normally has a free fatty acid (FFA) content of less than 0.1%, carotene content of less than 20 ppm and colour of less than 3 red in a 51/4" cell (Lovibond Scale). Prior art refining process of crude palm oil in summary involved, deodorising at temperatures between 240.degree. C.-260.degree. C. and at a pressure of 1-3 torr which processes resulted in not only the removal of unwanted fatty acids but also all carotenes being destroyed. .alpha.,.beta., Gamma and Zeta, zeacarotene, cis .alpha.-carotene, cis .beta.-carotene and lycopene are destroyed.
In prior art plant configurations, degassing of the crude palm oil and deodorizing of the degassed oil is done within the same equipment. The typical operating temperature is between 240.degree. C.-260.degree. C. At this temperature levels, unwanted free fatty acids (FFA) are removed, but in the process all carotenes are broken down. If the operating temperature is lowered, then FFA is not completely removed to meet the specification stipulated for edible oil and the end product is not completely deodorized and the taste is not bland.
In recent times attempts had been made to produce refined palm oil wherein the naturally occurring carotenes and Vitamin E are retained in substantially large quantities. Australia Patent No. AU-B-31084189 granted to Palm Oil Research Institute of Malaysia discloses an improved process for the refining of edible palm oil substantially without destroying the carotenes present in the oil which process comprises the step of subjecting the oil to a pressure of less then 0.060 Torr and a temperature of less than 200.degree. C. According to this invention palm oil or a product of palm oil is passed through a deodorizer, preferably at a temperature in the range 100.degree. C.-200.degree. C. and at a pressure in the range of 0.003-0.06 Torr. During this process the free fatty acids are distilled over and the oil deodorized, but the carotenes are not destroyed. This deodorized palm oil has a free fatty acid content of less than 0.12%. Carotene content and Peroxide values are almost the same as before the process. The refined oil has a bland smell. The examples disclosed in the said Australia patent, refer to laboratory scale reproductions of the invention. However on repeating the examples on a pilot plant scale or on a commercial plant scale showed different results. It was not possible to obtain yield of refined palm oil with the characteristics shown in Tables 1, 2, 3 or 4 of the AU Patent.
It is believed that gas, lights and free fatty acids at the molecular distillation stage create a strain on the distillation process. Increasing the operating temperature at the molecular distiller, reduces the level of FFA in the refined oil but at the same time destroys the carotene content in the oil. At operating temperatures of 100.degree. C.-200.degree. C. and at 0.003-0.060 Torr, all the FFA is not removed due to inefficient removal of condensed FFA in the condensation column.
Thus it is an object of this invention to provide a refining process wherein the FFA are removed to an acceptable level, the oil is deodorized to an acceptable level, the oil is rendered tasteless and the level of the carotene and Vitamin E present in crude palm oil substantially at levels exceeding 90% is retained in the refined oil.